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Penguins, Seals and Whales
Penguins are flightless birds found in the
Southern Hemisphere from the Antarctic to the equator. Of
the eighteen species, there are four that live in Antarctica
and they account for 85 percent of the region's bird population.
The Adelie and emperor breed on the Antarctic shores and
are the only two species found in the Ross Sea area. Chinstraps
breed on islands around Antarctica and gentoos are found
from the Antarctic islands to the sub-Antarctic. Another
three species (the King, rockhopper and macaroni) live on
the sub-Antarctic islands.
Penguins have to be well adapted to the cold.
They have short overlapping feathers (like tiles on a roof)
to minimise heat loss. Under the feathers is a layer of
down and beneath the skin is a thick layer of fat for extra
insulation. Their stocky bodies with small extremities (flippers,
feet and head) minimise body surface area over which heat
loss can occur. Heat loss from their feet is minimised while
they are standing. Their social behaviour also conserves
warmth - emperor penguins huddle together in large groups
during incubation and chicks of all species often group
together in creches.
Because ice covers almost all of Antarctica,
penguins have to get all their food from the sea where they
spend about half their time.
Adelie penguins can swim very quickly - up to 15 kilometres per hour. This gives them the momentum to leap out of the water onto the shore or ice floes. They can leap up to 2 metres, which is also a useful way to escape from predatory leopard seals.
The Adelie is the most numerous penguin in Antarctica. It stands 60-70 cm tall and weighs about 5.5 kg. Males and females look the same and have a black head, neck and back and a white ring around their eyes.
They spend the winter on the edge of the sea ice and come onto land in early spring, sometimes having to walk up to 50 kilometres over the ice to reach their nesting ground. They return to the same colony every year and usually to the same mate. The males arrive first and rebuild the nests. After mating, the female lays two eggs in early November and returns to the sea for 8-15 days while the males incubate the eggs. This means the males fast for about four weeks and lose about half their body weight by the time the females return and take over the incubating duty.
For the rest of the incubation period and
after hatching, they take turns to return to the sea to
feed for 2-3 days at a time. They bring back fish and krill
in their crops which they regurgitate to feed the chicks.
Emperors are the largest of all penguins.
They are about one metre tall and weigh approximately 30-40
kilograms. They have a black head, a bluey-grey neck with
a bright orange patch near the ears and pale yellow breast
fading into white.
The females return to the colony when the
chicks hatch and then both parents take turns crossing the
ice to the sea to feed and to bring back food for the chick. By January or early February the chicks lose their downy feathers
and, although not fully grown are ready to fend for themselves
in the sea. They spend their first two years at sea or on
the pack ice.
Four species of these carnivorous mammals live and breed in the Antarctic and are all found in the Ross Sea region. These four are "true" or earless seals, those without flaps on their ears. They are of course well adapted to the cold climate, with their big round bodies, layers of blubber and small extremities.
Seals catch most of their prey under water but spend some time on land or ice floes giving birth, raising their young and basking in the sun. On land they are quite ungainly but in the water they are very graceful and are excellent swimmers.
Much larger numbers of seals are found in
the Antarctic compared to the Arctic which reflects the
much greater abundance of food in the Southern Ocean.
Despite its name, the crabeater seal feeds
almost exclusively on krill which it strains through its
teeth. They are the most numerous of the Antarctic seals
and live on the pack ice. They reach up to 2.7 metres long and weigh over 250
kilograms, but little else is known about them.
More is known about Weddell seals because they live along the Antarctic coastline. In the winter though they spend a lot of time under the inshore sea ice because it is warmer in the water than in the air. They enlarge holes and cracks in the ice by chewing so they can come up for air and, in summer, to lie on the ice. They are about the same size as crabeaters. In spring groups of pregnant females and a male gather on the ice. A single pup is born which feeds on its mother's rich milk, which is the richest milk of any mammal.
They can dive to 600 metres in search of fish
and have specially adapted eyes for underwater vision in
low light levels.
Like crabeater seals, leopard seals are surface
feeders with krill an important part of their diet. They
also prey on penguins and other seal species and hunt for
fish and squid. Not much is known about their breeding habits.
They live mostly on the pack ice.
Ross seals are rarely found anywhere but on
floating ice and until 1963 less than 20 Ross seals had
ever been seen. Little is known about them but it is now
known that they are quite plentiful. They hunt squid and
fish at depths below the pack ice.
The killing of whales was one of the early reasons for venturing into Antarctic waters and claiming territory. In the early 1800s and then for another phase after gun powered harpoons were invented in 1870, whaling ships ventured south. About 1.3 million whales have been taken in Antarctic waters this century. Populations of the right, blue and humpback whales were decimated. It is estimated only about one percent of their original numbers survive. The fin and sei whales were also depleted to about 10-20 percent of their original population level.
The reduction in whale numbers began causing concern and in 1946 the International Whaling Commission (IWC) was established to regulate whaling operators, although this did not prevent continuing degradation of blue and humpback whale numbers or the serious depletion of the fin, sei and sperm whales.
With growing international concern for whales
blue and humpback whales were fully protected in 1963.
The long lived, slow breeding whales will take a long time to recover from past whaling pressures. It is thought the right and humpback whales may be recovering at the rate of up to seven percent a year but no increase has been noted in blue and fin whale populations.
A Southern Ocean Whale
Sanctuary was declared by the International Whaling
Commission in May 1994. The sanctuary extends from Antarctica
to 40°S, which includes New Zealand waters south of about
Wanganui. About 90 percent of the world's whales live in
this region and should now be safe from commercial whaling.
Japan, however, is still killing minke whales and hunted
in the Ross Sea region in 1995. The minkes are relatively
numerous, with an estimated population of about 760 000.
The blue whale, on the other hand, numbers only about 450,
down from its pre-whaling level of an estimated 250 000.
The whales do not live in Antarctica all year-round. They are found there in the summer, feeding on krill and other marine resources and in the autumn head north into the warmer waters of the tropics. There they give birth, the calf feeding on its mother's rich milk before migrating back to Antarctic waters.
Fourteen species of cetaceans (the name given to whales, dolphins and porpoises) are found in Antarctica. Of these, twelve are whales. There are two groups, the baleen whales and the toothed whales. Cetaceans are highly intelligent mammals. They communicate with sound which also serves as an echo location system.
Baleen is a huge hairy-edged plate in the whale's mouth which acts as a sieve. The whale sieves out krill, small fish and crustaceans.
Six species of baleen whales are found in Antarctica, including the huge blue whale which is the largest animal that has ever lived. It grows up to 24 metres and can weigh 84 tonnes. Other baleen species are the fin, southern right whale, sei, minke and humpback.
Four species of toothed whales are found in
Antarctica. Except for the sperm whale, they are much smaller
than the baleen whales and weren't widely hunted. The other
species are the southern bottlenose whale, the orca whale
and the southern
fourtooth whale. They all have teeth and feed on fish and
squid. The orcas also take penguins and seals.
Antarctica (2nd edition). Readers Digest. 1990.
Explore Antarctica. L. Crossley. Cambridge University Press. 1995.
The World of Penguins. C. Gaskin & N. Peat. Hodder & Stoughton. 1991.
Life in the Freezer. A. Fothergill. BBC Books. 1993.
Emperors of Antarctica. Wild South Video.
Icebird. Wild South Video.
Antarctica: A lonely planet travel survival kit. Jeff Rubin. 1996.